Brian Kelly stood on the sideline before the first snap of LSU’s win over Mississippi State on Saturday and saw something that ordinarily would be a concern — a true freshman lined up in the heart of his defense.

But Whit Weeks, a four-star linebacker from Georgia, looked comfortable. On the first play from scrimmage, he was the first Tiger in on a tackle of a Mississippi State receiver. And on the second, he diagnosed a run, navigated through a sea of bodies and burst into the backfield, hitting the running back 2 yards behind the line of scrimmage.

Against Mississippi State, a handful of freshmen played prominent roles. Mac Markway started at tight end in place of Mason Taylor. Ryan Yaites rotated in at safety with LSU’s nickel package. Kaleb Jackson made an emphatic case for more snaps with a violent 12-yard run. And Lance Heard continued to mix in with the first-team offensive line.

But none affected the game more so than Weeks, the younger brother of LSU junior linebacker West Weeks. The freshman was the Tigers’ leading tackler Saturday.

Collectively, the group has Kelly more confident in his team’s depth, particularly at linebacker and safety.

“You got three true freshmen on the field on the road in the SEC,” Kelly said. “I don't think you're running around going, ‘Oh, this is great.’ But we have confidence in them that they could go out and play well.”

Entering the Mississippi State game, Kelly knew that LSU had options on the defensive line. Jacobian Guillory and Jordan Jefferson would play meaningful snaps up front, spelling starters Mekhi Wingo and Maason Smith. And Bradyn Swinson would be ready to fill in as a Jack linebacker as needed.

But the absences of Omar Speights, who missed the game with an injury, and Greg Brooks, who was sidelined indefinitely by a medical emergency, forced LSU to test its depth at the other two levels of the defense for the first time this season.

Senior Andre Sam started in Brooks’ place at safety. Yaites, a four-star recruit from Texas, recorded two tackles in a rotational role, impressing Kelly with his discipline and intelligence.

The first thing that Kelly noticed about Weeks, on the other hand, was his speed, which Kelly said he uses to erase mistakes made along the defensive front and rush through gaps in the opposing offensive line. That, combined with a keen sense of coverage responsibilities, is why the younger Weeks started in place of Speights.

“He's not lost out there in pass coverage,” Kelly said. “And I would say that that probably is the reason why he's out there because he's not lost at anything. Can he get better in areas? Absolutely. But he makes up for a lot of that with high-end athletic ability.”

Weeks was part of a defensive front that let Mississippi State gain only 7 yards on its first five drives, hounding quarterback Will Rogers and stifling the run game.

LSU sacked Rogers four times, let him complete only 11 of 28 pass attempts and held his offense to only 94 yards rushing on 21 carries. If you exclude a 52-yard run by senior tailback Jo’Quavious Marks, then Mississippi State averaged only 2.1 yards per carry.

And in a stretch during Mississippi State’s first four drives, the LSU defense forced the Bulldogs to either lose yards or gain zero on 11 straight plays.

And the Tigers did it without two starters.

“I think our track record shows that the best players are going to play,” Kelly said. “And if you're a freshman, and you can handle it mentally and physically, we'll put you on the field.”

Email Reed Darcey at Reed.Darcey@theadvocate.com.